This application is related to Japanese Patent Applications No. 2000-385287 filed on Dec. 19, 2000, No. 2001-82180 filed on Mar. 22, 2001, No. 2001-87736 filed on Mar. 26, 2001, and No. 2001-334267 filed on Oct. 31, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electromagnetic valve used for a liquid-pressure control valve with a duty-ratio control, and an assembling method for fixing and assembling a movable core of the electromagnetic valve.
2. Description of Related Art
A conventional electromagnetic valve used for an oil-pressure control valve of an automatic changing gear is described in JP-A-10-292879. In the conventional electromagnetic valve 1, as shown in FIG. 9, a plunger 3 is supported in a shaft bearing 6 to be reciprocated with a movable core 2. An oil pressure of an operation oil flowing from an inlet port 5 is applied to a ball 4 toward the plunger 3 so that the ball 4 moves with the plunger 3. When electrical power is not supplied to a coil 7, the ball 4 seats on a valve seat 9 by spring force of a spring 8 for biasing the movable core 2, the plunger 3 and the ball 4 downwardly. Therefore, the ball 4 closes the inlet port 5, and an outlet port 11 communicates with a drain port 12. In this case, the oil pressure applied to a clutch or a brake decreases, and the clutch or the brake becomes a release state. On the other hand, when electrical power is supplied to the coil 7, the movable core 2 is moved toward a fixed core 14 against the spring force of the spring 8, and the ball 4 separates from the valve seat 9 and contact a valve seat 13. In this case, the high-pressure operation oil is supplied to the clutch or the brake, and the clutch or the brake becomes an engagement state.
However, in the conventional valve, the ball 4 is separated from the movable core 2 integrally fastened to the plunger 3, and the movable core 2 contacts the fixed core 14 by the electromagnetic attraction. Therefore, in duty-ratio control operation, vibration is transmitted from the fixed core 14 to a yoke 15, and relatively larger noise may be caused.
In addition, in order to accurately shut the communication between the outlet port 11 and the drain port 12 by using the ball 4, the stroke of the movable core 2 is set larger than that of the ball 4 by a predetermined distance, so that the ball 4 is sufficiently separated from the plunger 3. Thus, high-speed switching of the electromagnetic valve 1 is deteriorated by an unnecessary stroke required in the movable core 2, and a dynamic range with a linearity control in the relationship between a duty ratio and an output pressure becomes narrower. Further, in this case, the structure of a housing of the electromagnetic valve 1 becomes complex, and an assembling method thereof becomes difficult.
In view of the foregoing problems, it is an object of the present invention to provide an electromagnetic valve which prevents an inclination attachment and reduces noise.
It is an another object of the present invention to provide an electromagnetic valve having a wider dynamic range.
It is a further another object of the present invention to provide an electromagnetic valve which improves responsive performance relative to current switching operation.
It is a further another object of the present invention to provide an electromagnetic valve which reduces component number with a simple structure.
It is a further another object of the present invention to provide an assembling method of an electromagnetic valve, which can accurately attach a movable core to a shaft by simple operation.
According to a first aspect of the present invention, in an electromagnetic valve, a movable core is disposed in a housing opposite to a fixed core to be reciprocated in the housing, and a movable member is disposed to be reciprocated together with the movable core. The movable member includes a valve body for switching a communication between an inlet port and an outlet port and a communication between the outlet port and a drain port, and a shaft connected to both the movable core and the valve body. In addition, a coil for generating a magnetic attraction force for moving the movable core toward the fixed core is disposed, the shaft disposed to extend in an axial line has a radial dimension smaller than that of the valve body, the inlet port and the outlet port are provided in the housing in such a manner that the fluid flows into the housing from the inlet port in a direction along the axial line and flows out from the outlet port in a direction substantially perpendicular to the axial line, the fixed core and the movable core are disposed to have a maximum distance therebetween, the maximum distance is larger than a movable stroke of the movable member, and the movable core has a movable stroke that is controlled by the movable stroke of the movable member. Accordingly, in a case where the electromagnetic clutch is attached in a direction along the axial line, even when the fluid pressure of the outlet port is changed, the variation of the fluid pressure in the outlet port is applied in a direction perpendicular to the axial line, but is not applied to in a direction removing the electromagnetic valve. Thus, an inclination of the electromagnetic valve is prevented, and a frictional wear of a member for attaching the electromagnetic valve can be restricted. As a result, it is unnecessary to strengthen the attachment structure of the electromagnetic valve.
Because the movable stroke of the movable core is controlled by the movable stroke of the valve body, the movable core always does not contact the fixed core. Therefore, a generation of vibration of the fixed core can be prevented, and noise generated in the electromagnetic valve can be reduced. In addition, because the movable core does not contact the fixed core, a high-speed switching of the electromagnetic valve can be improved without providing an additional non-magnetic space between the movable core and the fixed core.
The housing has a first seat portion and a second seat portion opposite to the first seat portion. When the valve body contacts the first seat portion, the inlet port communicates with the outlet port, and a communication between the outlet port and the drain port is shut. On the other hand, when the valve body contacts the second seat portion, a communication between the inlet port and the outlet port is shut, and the outlet port communicates with the drain port. In addition, the shaft has a slidable portion slidable on an inner wall of the housing, and a small radial portion connected to the slidable portion and the valve body, and the drain port is provided in the housing around the small radial portion. Accordingly, component number of the electromagnetic valve can be reduced while the electromagnetic valve has a simple structure. As a result, the electromagnetic valve can be readily assembled using first and second assembling jigs. The first assembling jig includes a first position determination portion having a valve-body receiving chamber and a seat contact surface, and a second position determination portion having a standard end surface. In addition, the second position determination portion extends from a base position of the first position determination position to enclose the first position determination portion. Therefore, the assembling method of the electromagnetic valve can be made simple.
According to an another aspect of the present invention, in an electromagnetic valve, a maximum distance between a movable core and a housing is set larger than a movable stroke of a movable member, and a movable stroke of the movable core is controlled by the movable stroke of the movable member. Therefore, the movable core always does not contact the housing. Thus, generation of the vibration of the housing can be prevented, noise generated in the electromagnetic valve can be reduced. Accordingly, the electromagnetic valve is readily accurately assembled using an assembling jig.